Testing for positive infinity, or negative infinity, individually in Python

Question

math.isinf() tests for positive or negative infinity lumped together. What\'s the pythonic way to test for them distinctly?

Ways to test for positive infinity:

Answer 1

there is also numpy

>>> import numpy as np
>>> np.isneginf([np.inf, 0, -np.inf])
array([False, False,  True], dtype=bool)
>>> np.isposinf([np.inf, 0, -np.inf])
array([ True, False, False], dtype=bool)

and then there is general isinf

>>> np.isinf([np.inf, 0, -np.inf])
array([ True, False,  True], dtype=bool)

Answer 2

The "pythonic" way is to go with what's readable and maintainable.

That said, x == float("inf") and x == float("-inf") are slightly more readable to me, and I'd prefer them. math.isinf(x) and x > 0 is faster, but only on the order of about 40 nanoseconds per call.

So unless you're checking a whole lot of numbers, it isn't going to make much of a difference in running time.